The　ultrafine　WC-Co　composite　powder　was　synthesized　by　a　newly　developed　rapid　route　based　on　in　situ　reactions.　By　using　the　as-synthesized　composite　powder,　the　granulation　processing　was　then　carried　out　to　prepare　the　ultrafine-structured　thermal　spraying　feedstock.　The　influences　of　the　heat-treatment　process　on　density　of　the　feedstock　powder,　phase　constitution　and　wear　resistance　of　the　resultant　WC-Co　coatings　fabricated　by　high　velocity　oxy-fuel　(HVOF)　were　investigated.　The　results　showed　that　increasing　the　heating　temperature　and　extending　the　holding　time　leaded　to　remarkable　increase　in　the　density　and　flowability　of　the　feedstock　powder.　As　a　result,　the　decarburization　of　the　in-flight　particles　could　be　decreased　and　the　wear　resistance　of　coating　was　significantly　enhanced.　The　present　study　demonstrated　that　the　developed　techniques　for　the　ultrafine　powder　and　its　thermal-sprayed　coatings　had　very　promising　applications　in　scaling　up　to　produce　ultrafine-structured　cermet　coatings　with　excellent　performance.